It is well known in the art to use cipher algorithms to encrypt digital information. A cryptographic circuit which implements a cipher algorithm is generally constructed of hardware and is not changeable. By having the cipher algorithm fixed in hardware, the encryption process can readily be deciphered, thus to enhance the security of the encryption process, a changeable encryption key is used. The prior art discloses several ways of changing the encryption key.
It is also well known in the art that manufacturing of security sensitive cryptographic circuits must be done in a secure environment. This requirement substantially adds to the manufacturing costs. In addition to the increased costs, a cryptographic circuit cannot readily be modified to perform a different cipher algorithm. Thus, if the cipher algorithm has to be changed, a substantial redesign must be done.
A need exists for a cryptographic circuit that can be manufactured in a non-secure environment, that can be readily reprogrammed with a different cipher algorithm, and that enhances the security of the encryption process.